Impact of Antimicrobial Stewardship on Dairy Farm Welfare and Productivity: A Case Study

Thesis Abstract

The escalating threat of antimicrobial resistance within livestock production threatens dairy farm welfare, productivity, and public health, necessitating an evidence-based evaluation of antimicrobial stewardship (AMS) interventions in real-world dairy operations. This study investigates how AMS practices influence dairy health outcomes, welfare indicators, and production efficiency in a case-study of five large-scale cooperative dairy farms in a temperate region, each with over 1,500 milking cows and integrated veterinary oversight. The aim is to determine whether structured AMS programs improve animal welfare, optimize antimicrobial use, and sustain productivity while maintaining economic viability. Specific objectives are to (i) quantify baseline antimicrobial usage and resistance profiles on farm, (ii) evaluate welfare outcomes using the Welfare Quality-inspired on-farm assessment and lameness, body condition, and morbidity indicators, (iii) assess productivity metrics including milk yield, somatic cell count, feed efficiency, and days in milk, (iv) analyze adoption barriers and enablers of AMS among farm veterinarians and herd managers, and (v) model the relationship between AMS implementation, welfare indicators, and productivity using longitudinal data over 24 months. A mixed-methods design is employed, combining a quasi-experimental before-after approach with cross-sectional qualitative interviews. The population comprises all cattle across the five dairies, with a targeted sample of 2,000 lactating cows for phenotypic welfare and production data, 40 veterinarians and farm managers for semi-structured interviews, and 25 stocked farm records for antibiotic prescription data. Data collection instruments include standardized welfare assessment checklists, calibrated milking- and health-record templates, and validated questionnaires for attitudes toward AMS. Microbiological data are obtained through quarterly milk and environmental samples for susceptibility profiling against a panel of clinical isolates. Quantitative analyses employ multilevel mixed-effects regression to examine associations between AMS exposure (e.g., guideline-concordant prescriptions, duration of therapy, and prophylaxis reduction) and welfare/production outcomes, interrupted time-series analysis to detect changes in antimicrobial usage trends, and principal component analysis to summarize welfare composites. Economic evaluation uses cost-benefit and net present value calculations to relate AMS-related productivity changes to farm profitability. The qualitative component utilizes thematic analysis guided by the Normalization Process Theory and the Theory of Planned Behavior to elucidate adoption dynamics, with NVivo used for coding and triangulation across sources. Expected findings anticipate that robust AMS programs will reduce overall antimicrobial consumption by 25–40% without compromising clinical outcomes, reflected in lower total antibiotic DOT (days of therapy) and reduced antimicrobial resistance carriage in isolates. Welfare indicators are expected to improve or remain stable, with reductions in lameness prevalence and stress-related behaviors, alongside stable or enhanced milk yield and improved feed efficiency, driven by decreased disease incidence and optimized treatment regimes. The study also expects to identify key drivers of AMS uptake, including veterinary leadership, perceived economic benefits, and alignment with farm-scale workflow, while recognizing barriers such as perceived risk of under-treatment, inconsistent record-keeping, and variability in farmer trust. The study contributes to knowledge by providing empirical evidence on the causal pathways linking AMS practices to welfare and productivity in large dairy operations, integrating microbiological, clinical, economic, and behavioral perspectives within a single case framework. It advances understanding of context-specific AMS implementation, offers a transferable model for evaluating stewardship interventions across temperate dairy systems, and informs policy and extension programs on balancing animal welfare, antimicrobial stewardship, and farm profitability. The main conclusion is that well-implemented AMS, embedded within veterinary governance and farmer engagement, yields measurable welfare and productivity gains with favorable economic returns, while suggesting targeted recommendations standardize prescription protocols, strengthen antimicrobial use auditing, foster ongoing veterinary-farmer communication, enhance data systems for real-time monitoring, and promote farmer education on resistance risks. Recommendations for further research include multi-regional replication, longer-term sustainability assessment, and exploration of AMS impact on zoonotic risk transmission in dairy supply chains.